You have to remember JesusFan, that the GLC patrols space sectors and protect the universe from threats. The Heroes of Earth only protect Earth. In certain cases, they may protect other planets, but for the most part, they are limited to Earth affairs only.

So the GLC is definitely needed.

Except when the really bad like a Anti Moniter, or a darkseid rears up, they seem to be nowhere to be found!